1. Field of the Invention
The present invention relates to prosthetic limbs. More particularly, the present invention relates to strut system positioned between the upper leg and a prosthetic foot of an amputee which provides for increased rotation at the ankle joint and reduced rotation at the knee joint.
2. General Background
One of the inventors has obtained patents on first, a dual, ankle, springs prosthetic foot and ankle system, issued under U.S. Pat. No. 4,718,913, utilizing a pair of helical springs secured to a top ankle plant and to a plantar base plate. Placement of this system into a substantially rigid artificial foot, allowed, to a certain degree, normal walking movement, with the compression and elongation of the two springs depending on the various points in a walking movement. Likewise, a second patent, entitled Multi-axial Rotation System For Artificial Ankle, issued under U.S. Pat. No. 5,019,109, utilized a pair of compressible members, positioned in parallel relation, and attached to upper and lower plates, the assembly secured within a rigid artificial foot. The compressible members may be pre-compressed to provide the stepping movement during walking, similar to the '913 patent.
In both of these systems, the upper portion of the assembly would be rigidly attached to a lower leg prothesis, in order to complete the prosthetic assembly. However, in order to provide more normal walking ability, the lower leg, or calf prothesis had to be addressed. In the art, there exists device, patented under U.S. Pat. No. 4,822,363, entitled "Modular Composite Prosthetic Foot and Leg," which provides a prosthesis fabricated from laminants having a pylon with an upper extremity, a shin portion, an ankle portion and a forwardly extending foot portion, and a heel portion secured to the assembly. A second patent, U.S. Pat. No. 4,547,913, entitled "Composite Prosthetic Foot and Leg" which also utilizes high-strength fibers and has a unitary construction.
The patents cited above are provided in applicant's Prior Art Statement, which is being submitted herewith.